Speedometer drives

ABSTRACT

An apparatus disposed in a speedometer-odometer drive assembly for transferring and translating the rotation of a speedometer drive cable to a speedometer needle registering speed and an odometer registering distance, having an annular plate means disposed at one end of a drive shaft in communication with the speedometer cable and rotatable about a central axis with this shaft. The annular plate means is discontinuous at at least one point about its periphery by virtue of a cut or split generally directed toward its center, the facing edges of this cut or split being upset with respect to the radial plane of the surface of the annular plate means. These cut or split edges of the annular plate means act to engage successive threads or teeth on a gear means driving the odometer as the annular plate means rotates. Flanges are cut or formed from the surface of the annular plate means and bent to a position substantially perpendicular to the surface in such a manner that a magnet acting to drive the speedometer may be inserted between the flanges and the wall of a flux cup passed between the end of the magnet and each flange.

United States Patent 1 Bogosh June 19, 1973 i 5 SPEEDOMETER DRIVES [76] Inventor: Donald Bogosh, 2646 Willow,

Franklin Park, lll. 60131 [22] Filed: July 28, 1971 [21] App]. No.: 166,828

[52] U.S. Cl. 74/424.5, 74/12 [51] Int. Cl. F16h l/18, Fl6h 37/00 [58] Field of Search 74/12, 424.5;

[56] References Cited UNITED STATES PATENTS 1,872,288 8/1932 Helgeby 74/12 3,659,780 5/1972 Woodward 235/95 R Primary ExaminerLeonard H. Gerin Attorney-Robert E. Wagner [57] ABSTRACT An apparatus disposed in a speedometer-odometer drive assembly for transferring and translating the rotation of a speedometer drive cable to a speedometer needle registering speed and an odometer registering distance, having an annular plate means disposed at one end of a drive shaft in communication with the speedometer cable and rotatable about a central axis with this shaft. The annular plate means is discontinuous at at least one point about its periphery by virtue of a cut or split generally directed toward its center, the facing edges of this cut or split being upset with respect to the radial plane of the surface of the annular plate means. These cut or split edges of the annular plate means act to engage successive threads or teeth on a gear means driving the odometer as the annular plate means rotates. Flanges are cut or formed from the surface of the annular plate means and bent to a position substantially perpendicular to the surface in such a manner that a magnet acting to drive the speedometer may be inserted between the flanges and the wall of a flux cup passed between the end of the magnet and each flange.

10 Claims, 5 Drawing Figures PATENTED 9375 INVENTOR DONALD BOGOSH ATT'Y BACKGROUND OF THE INVENTION This invention relates to an improvement in speedometer drives and in particular to an apparatus forming an element of a speedometer-odometer assembly which transfers and translates the rotation of the speedometer drive cable to the remaining elements of the speedometer-odometer assembly.

Conventional speedometer-odometer assemblies for recording the speed and distance travelled by a moving vehicle are fairly simple mechanical devices including a threaded or worm drive shaft mounted on a frame and connected for rotation at one end with a speedometer drive cable being rotated by the revolving wheels of the vehicle, and having disposed at its opposite end a magnet which rotates with it. When the shaft is rotated by the speedometer drive cable, the threaded portion of the shaft engages the teeth of a crossover gear running substantially perpendicular to the shaft and imparts a rotation to this crossover gear. At the opposite end of the crossover gear are disposed circumferential threads, which engage and rotate, in a similar manner, the teeth at one end of an odometer worm drive gear. This odometer worm drive gear has threads at its opposite end engaging teeth disposed about the circumference of one of a series of numeraled odometer drums which register the revolutions of the wheels of the vehicle as distance for the benefit of the driver of the vehicle.

The magnet located at the forward or driving end of the rotating threaded shaft creates, upon rotation, a magnetic flux which causes the spring biased needle registering the speed of the vehicle to be held in a certain position with respect to a reference point, depending upon the speed of rotation of the speedometer cable and connected shaft.

The use ofa series of gears in the odometer assembly permits a significant reduction from the speed of rotation of the speedometer drive cable to the speed of rotation of the odometer numeral drum. The greater this gear reduction, of course, the lesser the chances of mechanical malfunction of the assembly and the greater the accuracy of the readings.

While the operative principle of the speedometerodometer drive assembly has been widely accepted, the problems and disadvantages in this assembly have become apparent in the production phase of these devices. The major problem lies in the threaded shaft or worm drive element connecting the speedometer drive cable to the speedometer-odometer assembly and driving the speedometer needle directly. This shaft, as described above, has, in the past, had to be formed having one end for connection with the speedometer drive cable, a threaded portion to impart a rotation to the crossover gear, and the opposite end adapted for receiving the magnet. Machining a shaft to meet these requirements is unsatisfactory from a manufacturing standpoint because of the time and materials and consequent large expense involved. In addition, the foreign made speedometer-odometer assemblies, while including the same type of gearing, can be produced at such a low cost that the U.S. assemblies using the standard cylindrically turned or machined worm drive or shaft are fast becoming non-competitive in the market.

DESCRIPTION OF THE INVENTION This invention involves an improvement in speedometer-odometer drive assemblies and in particular in the worm drive or threaded shaft element responsible for transferring the rotation of the speedometer drive cable to the odometer gear train and for translating the rotation of this cable to the speedometer needle to register speed. This improvement eliminates the necessity of machining this particular worm drive element and therefore greatly reduces the time and expense necessary to produce this element and the overall speedometer-odometer assembly without affecting quality and operation of the finished product. The worm drive apparatus of this invention accomplishes the same function as more expensive machined or cylindrically turned worm drive elements by an annular plate means or disc disposed on a drive shaft connected to the speedometer drive cable and rotatable therewith. This disc is split or cut from its periphery toward its center at at least one point about its circumference and the facing edges of the cut are one or both upset or separated with respect to the radial plane of the surface of the disc. The outside edge or periphery of the disc engages the teeth of a conventional odometer drive worm element of a speedometer-odometer assembly in such a manner that when the speedometer cable imparts a rotation to the drive shaft and the disc, the edge of the disc at the point of upset engages successive teeth on the odometer worm drive thereby causing it to rotate in the same manner as in a conventional drive train.

The annular plate means or disc is constructed by using a conventional washer and upsetting or splitting this washer in the manner described to form what is, in essence, a single revolution worm gear which is substituted for the conventional cylindrically turned or machined worm part. The cost saving effected by using this improved element in the speedometer-odometer drive assembly is felt to be substantial and sufficient to enable U.S. produced speedometer-odometer assemblies to become more nearly competitive with those imported from foreign countries and produced under less expensive labor conditions.

In addition, the annular plate means, which substitutes for the threaded portion or worm gear of the prior apparatus, may also be shaped in its surface, without machining, to receive the magnetic drive means necessary to produce the magnetic field driving the spring biased speedometer needle. This is done by cutting or forming two flanges from the surface of the disc and bending these flanges perpendicular to the surface on the opposite diameters so that a magnet may be placed between them, while providing a definite space between the inside surface of each flange and the end of the magnet. In this position, each flange allows the flux cup disposed over the magnet to pass between it and the end of the magnet as the flanges rotate with the disc about the circumference of the flux cup. Thus, the disc not only drives the odometer, but also serves to drive the speedometer.

Accordingly, it is an object of this invention to provide an improved speedometer-odometer drive assembly having an apparatus for connecting the speedometer drive cable to the odometer drive and the speedometer needle which requires no machining or cylindrical turning in its fabrication.

It is a further object of this invention to provide an apparatus for transferring and translating the rotation of a conventional speedometer drive cable to an odometer drive train and a speedometer needle without using a machined or cylindrically turned worm part and separate flux cup flange.

It is also an object of this invention to provide an apparatus for transferring the rotation of a speedometer drive cable to an odometer drive train and translating the rotation of a speedometer drive cable to a speedometer needle through a single revolution worm gear formed from a commercially available stock part.

These and other important objects of the invention will become apparent from the following description taken in conjunction with the drawings illustrating a preferred embodiment wherein:

FIG. 1 is a plan view of a speedometer-odometer assembly showing the improved drive train apparatus of this invention;

FIG. 2 is a side elevation view of a single revolution worm drive apparatus according to this invention as shown in FIG. 1;

FIG. 3 is a perspective view of the worm drive apparatus of this invention;

FIG. 4 is a top plan view of the worm drive apparatus of this invention; and,

FIG. 5 is a developed view of a double revolution worm drive apparatus according to this invention.

Referring now to the drawings, and more particularly to FIG. 1, there is shown a speedometer-odometer assembly generally at 10.

This assembly includes a frame 12 to support the elements of the assembly 10, and a hollow shaft or sleeve 14 providing a means for attaching the frame 12 and assembly 10 to the body of a vehicle. Disposed through the center of and surrounded by the hollow shaft or sleeve 14 is a drive shaft or spindle 16. This drive shaft or spindle 16 is freely rotatable about a central axis and is connected at its end not shown to a speedometer drive cable (not shown) providing a means to drive the apparatus of this invention. The drive shaft 16 has disposed at its opposite or inward end 18 an annular plate means or disc 20 which is fixedly attached to this inward end 18 for rotation with the drive shaft 16 about its central axis.

The annular plate means or disc 20 which forms the worm drive apparatus of this invention is discontinuous at at least one point about its periphery as shown in FIG. 3. This discontinuity is formed by a split or cut 22 which is generally inwardly directed toward the center of the disc 20 and the central axis of the drive shaft 16 supporting it. The facing edges 24 of the disc formed by this split or cut 22 are upset or axially spaced with respect to the plane of the radii of the disc 20 as shown in FIGS. 2 and 3 so that a distinct angle is formed between them or with the radial plane of the disc 20. The facing edges 22 lie in intersecting planes.

Annular plate means 20 has at least two opposite, facing flux cup flanges or tabs 26 formed or cut from its surface and bent substantially perpendicular to the plane of its radial surface. A magnet 28, shown in hidden lines in FIG. 1, is disposed between flux cup flanges 26 and adjacent to the surface of disc 20. The ends or poles of magnet 28, however, are separated slightly from the inside faces of flux cup flanges 26 to allow the outside wall of cylindrical flux cup 30 to pass between the ends of magnet 28 and the inside faces of flux cup flanges 26.

Flux cup 30 includes an inverted cylinder of soft metal, open at its end brought adjacent disc 20, which is disposed over magnet 28 and between flux cup flanges 26. Flux cup 30 has a speedometer axle 32 disposed through its closed top end, one end of which is placed in a recessed top portion of the drive shaft 16 so that the speedometer axle 32 and flux cup 30, which is fixedly attached thereto, may rotate freely with respect to drive shaft 16 but about the same central axis. Axle 32 is biased by a spring means 34 on the outside of the frame 12 so that when drive shaft 16 is not rotating axle 32 and flux cup 30 are returned to the same original position or reference point. The end of speed ometer axle 32 extending beyond spring means 34 is attached to a speedometer needle (not shown) which registers speed on a gauge visible to the operator of the vehicle. Thus, when the vehicle is not moving, flux cup 30 and axle 32 are returned to their original position and the needle on the gauge reads zero.

The annular plate means or disc 20 of this invention also operates upon an odometer drive worm 40 which includes a cylindrical shaft 42 disposed between the front and back ends of the frame 12, freely rotatable about a central axis. The shaft 42 has a helical gear 44 adjacent disc 20, having a plurality of teeth disposed about its circumference which are engaged by the peripheral edge of disc 20 as the disc 20 rotates about the central axis of shaft 16.

The odometer drive worm 40 has, formed about the circumference of the shaft 42 at its opposite end, a machined or cylindrically turned worm portion 48, the threads of which engage the teeth 52 disposed about the circumference of the outermost drum in a series of cylindrical odometer numeral drums. In this manner, odometer numeral drums 50 may be successively rotated on an axle 54 extending through their centers and between the sides of frame 12.

In the operation of this speedometer-odometer assembly 10 using the improved apparatus of this invention, the speedometer cable (not shown) receives a rotation from one of the wheels of the moving vehicle. This speedometer cable, in communication with drive shaft or spindle l6, imparts this rotation to shaft 16 so that the shaft 16 is rotated about its central axis. As the shaft 16 is rotated, the annular plate means or disc 20 which is fixedly attached to the inward end 18 of drive shaft 16 is similarly rotated about this same central axis. Thus, the magnet 28 which is likewise attached to shaft 16 or the surface of disc 20 is rotated about this central axis within flux cup 30. As magnet 28 is so rotated within flux cup 30 and flux cup flanges or tabs 26 are moved about the outside wall of cylindrical flux cup 30, a magnetic force field is created within said flux cup, the strength of which increases in proportion to the speed of rotation of the shaft 16. Since the flux cup 30 is fabricated of soft metal, it ordinarily dissipates the flux lines created by a magnetic field as soon as the magnetic field is removed. However, when the magnet producing the field is rotated at a high speed, such flux lines do not dissipate in the brief interval of time between their first creation by the magnetic field and the later return of the field. Thus, the force lines retained in the soft metal of the flux cup 30 are increased with the speed of rotation of the shaft 16 and the magnet 28. As the speed of rotation of the shaft 16 is increased and the strength of the magnetic force field is increased, the flux cup is rotated with speedometer axle 32 to the extent that the increasingly more uniformly distributed magnetic field developed about the interior circumference of the flux cup 30 overcomes the oppositely directed force of spring means 34. As the force of spring means 34 is overcome, the flux cup 30 is moved to a position in direct relationship to the force of the spring means and the speed of the rotation of the shaft 16. The speedometer needle (not shown), which is attached to the projecting end of speedometer axle 32, then indicates to the operator of the moving vehicle the approximate calibrated speed at which the vehicle is moving.

In the operation of the odometer means from the same apparatus of this invention, the annular plate means 20, rotating about the speedometer drive shaft 16, is placed in a position within frame 12 adjacent to worm shaft 42 so that the periphery or edge of disc 20 is disposed in the space or groove between the teeth 46 of gear 44. As the disc 20 rotates about the central axis of shaft 16, it imparts a rotation to a gear 44 and worm shaft 42, since, at the point of discontinuity on the disc 20 caused by the split or cut 22, the facing edge 24 is upset or axially spaced a definite distance from the lower facing edge 24. Thus, when this point of discontinuity is reached, the upper facing edge 24 engages the space or groove on the opposite side, of the next succeeding tooth 46 on the gear 44 as shown in FIG. 2, causing the attached shaft 42 to be rotated about its central axis.

The worm portion 48 of the odometer drive worm also rotates about this central axis engaging successive teeth 52 on the odometer numeral drum 50, thus imparting a rotation to the drum 50. Obviously, the speed of rotation of the numeral drums about axle 54 is much less than the speed of rotation of speedometer drive shaft 16 since the series of gears causes a reduction in speed of approximately 1,000 to 1. Such a reduction provides not only for much less strain on successive operating gears and shafts in the drive train, but also for greater accuracy in measuring distance.

FIG. 5 represents another possible embodiment of the unique split worm drive apparatus of this invention. This shows a modified form of this apparatus called a double revolution worm gear. That is, the facing edges 24 formed by the split or cut 22 in the embodiment described above are simply, in this embodiment, split or upset with respect to the radial plane of the surface of the annular plate means 20 equal distances above and below this plane. Thus, for each revolution of this modified form of disc 20 on shaft 16, the disc 20, at the point of discontinuity, will engage every other succeeding tooth 46 on gear 44 causing worm drive shaft 42 to be rotated twice as fast around its central axis and the consequent gear reduction to be approximately 500, to

FIGS. 3 and 4 show the disposition and configuration of the flux cup flanges or tabs 26. Both flanges are uniform with respect to one another so that the magnetic flux created in the soft metal of the flux cup 30 may likewise be uniform.

The apparatus of this invention may be constructed of any suitable material which is hard, resistant to wear, and may be easily cut and slightly bent into the desired shape, such as stainless steel or stainless steel alloys.

The flux cup, as stated previously, should be constructed of a soft metallic substance so that it is prone to accept and release a magnetic field quickly.

The other gears and numeral drums in the speedometer-odometer assembly have been in the past formed from wear resistant durable material such as stainless steel alloys or high impact plastics.

While the invention has been described in relation to preferred embodiments thereof, it will be apparent to those skilled in the art that the structural details are capable of wide variation without departing from the principles of the invention.

I claim:

1. An apparatus particularly adapted for use in a speedometer and odometer drive assembly, said apparatus including a frame, an annular plate means disposed for rotation in said frame, an odometer worm drive means mounted for rotation in said frame, and

means to drive said annular plate means, said annular plate means having at least two axially extending flux cup flange means formed integrally therewith, said flange means being formed on opposite diameters of said plate means, said flange means serving to magnetically couple said speedometer by partially surrounding a magnetic drive means supported on said frame, said magnetic drive means being axially spaced from said annular plate means, said annular plate means being discontinuous at at least one point on its periphery, the facing edges of said annular plate means at the point of discontinuity being axially spaced relative to the radial plane of said annular plate means for engagement with successive teeth or threads of said worm drive means to impart a rotation to said drive means as said annular plate means is rotated, thereby driving said odometer.

2. The apparatus of claim I wherein said means to drive said annular plate means includes a shaft supported on said frame and rotatable about a central axis, said shaft connected at one end to a. speedometer drive cable and having said annular plate means fixedly mounted at its opposite end for rotation therewith about said central axis.

3. The apparatus of claim 1 wherein said annular plate means includes a substantially flat disc which has been made discontinuous by a split or cut generally extending inwardly from the periphery of said disc toward the center thereof, at least one of said facing edges formed in said disc by said split or cut being axially spaced or upset with respect to the radial plane of said disc in such a manner that said edges lie in diverse planes and allow said disc to engage successive teeth or threads disposed about the circumference of said odometer worm drive means to impart a rotation to said drive means as said disc is rotated with said means to drive said annular plate means.

4. The apparatus of claim 1 wherein said flux cup flange means include tabs cut from said annular plate means on opposite sides of the center of said annular plate means, each of said tabs being bent to a position substantially perpendicular to radial plane of said annular plate means in such a manner that said tabs are maintained in spaced relationship to said magnetic drive means and partially surround said magnetic drive means.

5. The apparatus of claim 1 wherein said magnetic drive means includes a magnet axially spaced from the surface of said annular plate means, disposed between said flux cup flange means and rotatable with said annular plate means on said means to drive said annular plate means, and cylindrical flux cup means insertable over said magnet and between said flux cup flange means, the walls of said flux cup means passing between each end of said magnet and each of said flange means as it rotates on an axis supported on said frame.

6. In an apparatus particularly adapted for use in a speedometer-odometer drive assembly and including a frame, a speedometer drive shaft mounted for rotation in said frame and a speedometer drive cable which imparts a rotation to said speedometer drive shaft, a magnetic drive means rotatable in said frame to create a magnetic force field acting on a speedometer registering distance, the improvement comprising, annular plate means disposed near one end of said speedometer drive shaft and rotatable therewith, said annular plate means having integral flux cup flange means extending axially therefrom, said flange means partially surrounding said magnetic drive means being maintained in axially spaced relation with respect to said annular plate means, said annular plate means being discontinuous at at least one point on its periphery, the facing edges of said annular plate means at the point of discontinuity being axially spaced relative to the radial plane of said annular plate means in such a manner that said annular plate means engages successive teeth or threads of said odometer worm drive means thereby imparting a rotation to said odometer worm drive means as said annular plate means is rotated, thereby driving said odometer.

7. The improvement set forth in claim 6 wherein said speedometer drive shaft is rotatable about a central axis and has said annular plate means fixedly mounted at one end thereof for rotation about said central axis therewith.

8. The improvement set forth in claim 6 wherein said annular plate means includes a substantiallyflat disc in which said discontinuity has been formed by a split or cut extending generally inwardly from the periphery of said disc toward the center thereof, at least one of said facing edges formed in said disc by said split or cut being axially spaced or upset with respect to the radial plane of said disc in such a manner that said edges lie in diverse planes and allow said disc to engage successive teeth or threads disposed about the circumference of said odometer worm drive means thereby imparting a rotation to said w'orm drive means as said disc is rotated.

9. The improvement set forth in claim 6 wherein said flux cup flange means include tabs cut from said annular plate means on opposite sides of the center of said annular plate means, said tabs being bent to a position substantially perpendicular to the radial plane of said annular plate means in such a manner that said tabs are maintained in spaced relationship to said magnetic drive means and partially surround said magnetic drive means.

10. The improvement set forth in claim 6 wherein said magnetic drive means includes a magnet disposed between said flux cup flange means, axially spaced from the surface of said annular plate means and rotatable with said annular plate means on said means to drive said annular plate means, and cylindrical flux cup means insertable over said magnet and between said flux cup flange means, the walls of said flux cup means passing between each end of said magnet and each of said flange means as it rotates on an axis supported on said frame. 

1. An apparatus particularly adapted for use in a speedometer and odometer drive assembly, said apparatus including a frame, an annular plate means disposed for rotation in said frame, an odometer worm drive means mounted for rotation in said frame, and means to drive said annular plate means, said annular plate means having at least two axially extending flux cup flange means formed integrally therewith, said flange means being formed on opposite diameters of said plate means, said flange means serving to magnetically couple said speedometer by partially surrounding a magnetic drive means supported on said frame, said magnetic drive means being axially spaced from said annular plate means, said annular plate means being discontinuous at at least one point on its periphery, the facing edges of said annular plate means at the point of discontinuity being axially spaced relative to the radial plane of said annular Plate means for engagement with successive teeth or threads of said worm drive means to impart a rotation to said drive means as said annular plate means is rotated, thereby driving said odometer.
 2. The apparatus of claim 1 wherein said means to drive said annular plate means includes a shaft supported on said frame and rotatable about a central axis, said shaft connected at one end to a speedometer drive cable and having said annular plate means fixedly mounted at its opposite end for rotation therewith about said central axis.
 3. The apparatus of claim 1 wherein said annular plate means includes a substantially flat disc which has been made discontinuous by a split or cut generally extending inwardly from the periphery of said disc toward the center thereof, at least one of said facing edges formed in said disc by said split or cut being axially spaced or upset with respect to the radial plane of said disc in such a manner that said edges lie in diverse planes and allow said disc to engage successive teeth or threads disposed about the circumference of said odometer worm drive means to impart a rotation to said drive means as said disc is rotated with said means to drive said annular plate means.
 4. The apparatus of claim 1 wherein said flux cup flange means include tabs cut from said annular plate means on opposite sides of the center of said annular plate means, each of said tabs being bent to a position substantially perpendicular to radial plane of said annular plate means in such a manner that said tabs are maintained in spaced relationship to said magnetic drive means and partially surround said magnetic drive means.
 5. The apparatus of claim 1 wherein said magnetic drive means includes a magnet axially spaced from the surface of said annular plate means, disposed between said flux cup flange means and rotatable with said annular plate means on said means to drive said annular plate means, and cylindrical flux cup means insertable over said magnet and between said flux cup flange means, the walls of said flux cup means passing between each end of said magnet and each of said flange means as it rotates on an axis supported on said frame.
 6. In an apparatus particularly adapted for use in a speedometer-odometer drive assembly and including a frame, a speedometer drive shaft mounted for rotation in said frame and a speedometer drive cable which imparts a rotation to said speedometer drive shaft, a magnetic drive means rotatable in said frame to create a magnetic force field acting on a speedometer registering distance, the improvement comprising, annular plate means disposed near one end of said speedometer drive shaft and rotatable therewith, said annular plate means having integral flux cup flange means extending axially therefrom, said flange means partially surrounding said magnetic drive means being maintained in axially spaced relation with respect to said annular plate means, said annular plate means being discontinuous at at least one point on its periphery, the facing edges of said annular plate means at the point of discontinuity being axially spaced relative to the radial plane of said annular plate means in such a manner that said annular plate means engages successive teeth or threads of said odometer worm drive means thereby imparting a rotation to said odometer worm drive means as said annular plate means is rotated, thereby driving said odometer.
 7. The improvement set forth in claim 6 wherein said speedometer drive shaft is rotatable about a central axis and has said annular plate means fixedly mounted at one end thereof for rotation about said central axis therewith.
 8. The improvement set forth in claim 6 wherein said annular plate means includes a substantially flat disc in which said discontinuity has been formed by a split or cut extending generally inwardly from the periphery of said disc toward the center thereof, at least one of said facing edges formed in said disc by said split or cut being axially spaced or upset With respect to the radial plane of said disc in such a manner that said edges lie in diverse planes and allow said disc to engage successive teeth or threads disposed about the circumference of said odometer worm drive means thereby imparting a rotation to said worm drive means as said disc is rotated.
 9. The improvement set forth in claim 6 wherein said flux cup flange means include tabs cut from said annular plate means on opposite sides of the center of said annular plate means, said tabs being bent to a position substantially perpendicular to the radial plane of said annular plate means in such a manner that said tabs are maintained in spaced relationship to said magnetic drive means and partially surround said magnetic drive means.
 10. The improvement set forth in claim 6 wherein said magnetic drive means includes a magnet disposed between said flux cup flange means, axially spaced from the surface of said annular plate means and rotatable with said annular plate means on said means to drive said annular plate means, and cylindrical flux cup means insertable over said magnet and between said flux cup flange means, the walls of said flux cup means passing between each end of said magnet and each of said flange means as it rotates on an axis supported on said frame. 